<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>消除空格</title>
</head>
<body>
    <script>
        const s = ' welcome ';

        console.log(s.trim()); //"welcome"
        console.log(s.trimStart()); //"welcome "
        console.log(s.trimEnd()); //" welcome"
    </script>
</body>
</html>